A guy who thinks he's far funnier and more intellectual than he really is. The type who starts pretentiously clever discussions in order to make women think he's smart, when really, he's just average.
When referring to theman who engages this behaviour, he is referred to as "breakwall"; when engaging in this behaviour, the verb is "to breakwall".

"She never noticed him before, but she totally fell for his breakwall when he started that thread on how birth control is good for World Peace".